Strain Selection in Gracilaria spp. I. Growth, Pigment, and Carbohydrates Characterization of Strains of G. conferta and G. verrucosa (Rhodophyta, Gigartinales)

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Abstract
Four local strains of Gracilaria cf. conferta and a foreign strain of G. verrucosa were grown under outdoor and laboratory conditions. Growth as well as morphology, chlorophyll a (CHL) content, agar and carbohydrate characteristics were observed. One local male gametophytic strain (SGY-2) produced the highest agar gel strength (> 900 g cm-2) and CHL content. This strain exhibited the highest productivity, and was also highly resistant to epiphytes. Growth experiments under various photon flux densities (PFD) and temperature combinations on the gradient table revealed that a high temperature resistance and a higher light saturation point characterized the foreign G. verrucosa strain as compared with local strains. Growth performance were mostly temperature-dependent, whereas carbohydrate features and CHL content were PFD-dependent. It has been found that growth rate was the major feature which dominated the changes in the galactose monthly yield. Other factors, such as carbohydrate content, dry weight content, and galactose/glucose ratio, were of secondary influence on the galactose yield. The relationships between growth, morphology and agar quality are discussed.